Centrifugally armed fuze



Feb. 4, 1969 o. CARLSON 3,425,354

GENTRIFUGALLY ARMED FUZ E Filed Oct. 30, 1967 I NVENTOR. DONOVAN CARLSONAT TORNE Y 3,425,354 CENTRIFUGALLY ARMED FUZE Donovan Carlson,Minneapolis, Minn., assignor to Honeywell Inc., Minneapolis, Minn., acorporation of Delaware Filed Oct. 30, 1967, Ser. No. 678,910 US. Cl.10279 Int. Cl. F42c 9/06, 15/26 4 Claims ABSTRACT OF THE DISCLOSUREBackground of the invention Field of the invention.Percussive orelectric fuzes wherein the fuze is armed by inovement of a member whichresponds centrifugally to rotation of the shell (CL 102-79).

Description of the prior art.Centrifugal arming is quite well-known inthe prior art. Most centrifugal arming arrangements, however, comprisedof mechanical locks and weights. Fluid is utilized in some cases for thepurpose of delaying the operation of the fuze. Examples of the prior artare Patents 2,641,186 to Apotheloz and 3,118,379 to Jasse. The applicantis not, however, aware of any prior art wherein fluid is used as apositive force in the arming sequence of a centrifugally armed fuze.

Summary of the invention The present invention provides for an armingand time delay mechanism for spin operated fuzes. Its unique feature isthat it employs a buoyant slider member mounted in a fluid-filledhousing. In the unarmed condition the slider member is held away fromthe axis of rotation by a spring and by centrifugal looks or othersuitable safing mechanisms. The space around the slider member is filledwith a fluid having long-term stability and a relatively uniformviscosity over a broad temperature range. The fluid has adequate densityto float the slider assembly.

The fuze is spin actuated. The centrifugal locks are are released underspin environment, releasing the slider member. Under the spinconditions, the fluid is displaced outwardly, away from the axis ofrotation, and the buoyant slider is forced by the fluid inwardly towardthe axis of rotation. The slider member carries an explosive detonator,which upon actuation is carried by the slider member into a position inline with a firing pin and a pyrotechnic chain.

It is therefore an object of the present invention to provide animproved centrifugally armed fuze. A further object of the presentinvention is to provide a centrifugally armed fuze wherein a fluid isused to provide a positive force in the arming sequence. These andfurther objects will become apparent to those skilled in the art uponexamination of the following specification, claims, and the drawing.

A brief description of the drawing FIGURE 1 is a cross-sectional view ofa typical embodiment of the fuze according to the present invention,looking along the spin axis from the top of the fuze;

States Patent 3,425,354 Patented Feb. 4, 1969 FIGURE 2 is a simplifiedschematic representation of the embodiment of FIGURE 1;

FIGURE 3 is a sectional side view taken along line 3-3 of FIGURE 1;

FIGURE 4 is a simplified schematic. representation of the sectional sideview of FIGURE 3; and

FIGURE 5 is a similar sectional side view, but with the fuze in thearmed position.

Detailed description Referring now to FIGURE 1, a cross-sectional viewof the fuze is shown out along a plane perpendicular to the axis ofrotation. The fuze has an outside fuze housing 10. Within fuze housing10 is mounted a delay housing 12. Delay housing 12 defines a cylindricalcavity -13 whose axis intersects the axis of rotation and lies in aplane substantially perpendicular to the axis of rotation. Cavity 13extends from one side of housing 10 across the center of housing 10, acertain distance beyond the axis of rotation. Within cavity 13 ismounted a buoyant slider piston 14. Slider piston 14 is biased towardsthe end of cavity 13 which is nearest the outside wall of housing 10.The biasing is accomplished by a light spring 15 located between sliderpiston 14 and a closure member 16 which defines the inner end of delayhousing 12.

Slider piston 14 carries a detonator 18 at a position which is away fromthe axis of rotation while the slider piston is in its normal positionadjacent to the outside wall of housing 10. The entire internal cavityof delay housing 12 is filled with a fluid 20. Fluid 20 is chosen for along-term stability and a relatively uniform viscosity over a broadtemperature range. The relative density of fluid 20 to slider piston 14is such that slider piston 14 will float. To give slider piston 14sufiicient buoyancy, the slider piston can be provided with a hollowcavity 21, such as shown in FIGURE 1. Cavity 21 is shown being sealed bya cover 22.

At the inner most end of slider piston 14, a seal 17 is placed aroundthe periphery of slider'member 14, adjacent to the internal walls ofdelay housing 20. The purpose of seal 17 is to prevent uncontrolled flowof fluid 20 from one side to the other side of slider piston 14. Ametering orifice 19 is, however, provided to allow the flow of fluid 20from one side to the other side of slider piston 14 at a controlledrate.

A pair of centrifugal locks 24 and 25 are mounted Within delay housing12 and are adapted to engage with slider piston 14 to prevent the motionof piston 14 prior to a predetermined threshold of angular rotationabout the fuze axis of rotation.

A more clear understanding of the apparatus of FIG- URE 1 will beachieved by referring to FIGURE 3. FIG- URE 3 shows a cross-section of aside view cut along lines 3-3 of FIGURE 1. Delay housing 12 is shownheld between a forward housing member 28 and a rear housing member 29.Formed in the rear housing member 29, concentric with the axis ofrotation, is an opening 30 within which is located a lead cup or boostercharge 31. An opening 32 is formed in forward housing member 28, opening32 being centrally located and coaxial with opening 30 on rear housingmember 29. Mounted within opening 32 is a firing pin 34. Firing pin 34has a first flange 35 formed adjacent the pointed end thereof, toprevent the firing pin 18 from being forced out of opening 17. A secondflange 36 is connected to the opposite end of firing pin 34 by a screw37. Mounted between flange 36 and forward housing member 28 is a coiledspring 38 which tends to hold firing pin 34 in the position shown inFIGURE 3.

The simplified schematics of views 2, 4, and 5 will be helpful inunderstanding the operation of the invention.

Operation In the unarmed condition, buoyant slider piston 14, carryingdetonator 18, is held away from the axis of rotation by centrifugallocks 24 and 25. If redundancy is desired for additional safety, setbacklocks can also be added although they are not shown in the embodimentsof FIGURES 1 and 2. The space surrounding slider piston 14 is filledwith a fluid such as Dow Corning Silicone 200, which has a long-termstability, has a relatively uniform viscosity over a broad temperaturerange, and is of adequate density to float slider piston 14. Thedisplacement away from the axis of rotation of lock weights ofcentrifugal locks 24 and 25 under the spin environment releases sliderpiston 14. Under spin conditions the fluid is displaced outwardlythrough orifice 19 at a rate de pending on rotational velocity andorifice size. The resulting buoyant force acting on the slider membermoves it toward the in-line position against a light return spring 15.

Delay time will depend on the viscosity of the fluid and hence ontemperature. The use of a very short orifice causes the flow rate tofollow the Bernoulli equation, and minimizes the flow restriction due tothe viscous shearforces, thus yielding a delay that is inverselyproportional to the spin rate and relatively insensitive to temperature.The delay time can be controlled by varying the spring biasing andvarying viscosity of the fluid.

Although centrifugal locks are shown in FIGURE 1 for holding the sliderprior to the operation of the fuze, these may not be necessary becauseof the force-time integrating features of the dash-pot system. A setbacklock pin may be more appropriate.

A unique feature of the present invention, as compared to prior artfluid delays, is that in case of loss of fluid from the system, the fuzewill remain in a fail-safe condition. This is an advantage of greatimportance, as will be obvious to those who are familiar with the safetyhazards in the area of fuzing art.

The following functioning sequence places the fuze from a unarmed to anarmed position. Centrifugal locks 24 and 25 are released by centrifugalforces above a safety threshold. Fluid 20 is displaced radially throughmetering orifice 19 by a centrifugal force at a rate dependent uponprojectile spin and orifice size. The slider floats toward armedposition, snapping in line when seal 17 passes over arming grooves 40and 41, thus permitting a sudden increase in fluid flow rate.

Obvious advantages of the present invention are that it is extremelysimple in operation and is therefore highly reliable. It has the uniquesafety feature that it is impossible to prematurely arm and has highresistance to rough handling environments.

From the above description it will be apparent that I have invented amunition fuzing concept having new and more effective means forutilizing the centrifugal force developed by a rotation munition forarming purposes and providing safety in handling.

I claim:

1. An arming and time delay mechanism for spin operated fuzescomprising:

a fuze housing defining a hermetically sealed chamber filled with arelatively high density fluid;

a buoyant slider positioned in said fluid within said chamber, saidslider having a freedom of motion along a line substantiallyperpendicular to the spin axis of the fuze;

an explosive detonator mounted on said slider; and

locking means mounted in said housing for holding said slider away fromthe axis of rotation when said fuze is in an unarmed condition, and torelease said slider for motion toward the axis of rotation in responseto fluid pressure exerted on said slider, in line with a firing pin andpyrotechnic chain, after the fuze is subjected to an angular rotation.

2. An arming and time delay mechanism for a spin operated munition fuzecomprising:

a fuze housing having an axis of rotation;

a firing pin and an explosive lead cup mounted in said housing centeredon said axis of rotation;

a delay housing mounted within said fuze housing, said delay housingdefining a hollow hermetically sealed chamber of generally cylindricalshape with its axis substantially perpendicular to said axis ofrotation;

a slideable piston member mounted within said delay housing, said pistonmember subdividing the sealed chamber of said delay housing into a firstchamber toward said axis of rotation and a second chamber away from saidaxis of rotation, said piston member further having a fluid passage toallow fluid transfer between said two chambers;

a fluid filling said sealed chamber of said delay housing, said fluidhaving suflicicnt density to float said piston member;

a detonator mounted on said piston member; and

safing means mounted in said delay housing for holding said pistonmember away from the axis of rotation when said fuze is in an unarmedstate, and to allow said piston member to move toward the axis ofrotation when said fuze is caused to spin about its axis of rotation inresponse to fluid flow from said first chamber to said second chamber toarm the fuze by bringing said detonator in line with said firing pin andsaid explosive lead cup.

3. Apparatus according to claim 2 wherein said safing means includes aspring for biasing said piston member away from the axis of rotation.

4. Apparatus according to claim 3, wherein said safing means furtherincludes centrifugal locking means for maintaining said slideable pistonlocked in a safe position until said fuze is caused to spin about itsaxis of rotation in excess of a predetermined angular rate.

References Cited UNITED STATES PATENTS 527,250 10/ 1894 Smith 102-823,118,379 1/1964 Jasse 102-79 3,264,995 8/1966 Libby et al 102-793,296,969 1/ 1967 Mueller et a1. 102-82 FOREIGN PATENTS I 129,041 7/1919 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner. GERALD H. GLANZMAN, AssistantExaminer.

US. Cl. X.R. 102-82

